PTC refers to PVUSA Test Conditions,
which were developed to test and compare PV systems as part of the
PVUSA (Photovoltaics for Utility Scale Applications) project. PTC are
1,000 Watts per square meter solar irradiance, 20 degrees C air
temperature, and wind speed of 1 meter per second at 10 meters above
ground level. PV manufacturers use Standard Test Conditions, or STC,
to rate their PV products. STC are 1,000 Watts per square meter solar
irradiance, 25 degrees C cell temperature, air mass equal to 1.5, and
ASTM G173-03 standard spectrum. The PTC rating, which is lower than
the STC rating, is generally recognized as a more realistic measure of
PV output because the test conditions better reflect "real-world"
solar and climatic conditions, compared to the STC rating. All ratings
in the list are DC (direct current) watts.

Neither PTC nor STC account for all
"real-world" losses. Actual solar systems will produce lower outputs
due to soiling, shading, module mismatch, wire losses, inverter and
transformer losses, shortfalls in actual nameplate ratings, panel
degradation over time, and high-temperature losses for arrays mounted
close to or integrated within a roofline. These loss factors can vary
by season, geographic location, mounting technique, azimuth, and array
tilt.

IMPORTANT !

The advertised system prices that are
quoted on this website are based on the our system's DC or STC
wattage ratings not their AC wattage rating. Please note that
because a solar system's estimated AC power production is site and
installation dependent, we do not post our system's estimated AC
wattage ratings. To calculate the estimated AC wattage rating of
your chosen solar system, multiply the PTC rated output of the solar
panels by the number of solar panels multiplied by the CEC weighted
efficiency of the inverter, multiplied by the system's design factor
which is based on module tilt angle, azimuth angle, shading and
geographic location. Other factors that can affect your chosen solar
system's AC wattage rating are: Solar module soiling, module
mismatch, wire losses, inverter and transformer losses, shortfalls
in actual nameplate ratings, solar panel degradation over time, and
high-temperature losses for arrays mounted close to or integrated
within a roofline.

If you wish to be provided with a solar
system's estimated AC power production, please ask your sales
representative to provide you with an estimate or you can visit the
following web pages and gather your specific solar panel's PTC
rating and inverter CEC weighted efficiency and use the following
formula to estimate a solar system's AC wattage production:

Multiply the PTC rated output of the
solar panels by the number of solar panels multiplied by the CEC
weighted efficiency of the inverter, multiplied by your system's
design factor which is based on module tilt angle, azimuth angle,
shading and geographic location.